Organic hexamethine compound



Patented Mar. 3, 1942 ORGANIC HEXAMETHINE COMPOUND Walter Zeh, Dessau, Anhalt, Germany, assignor, by mesne assignments, to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware N Drawing. Application June 22, 1937, Serial Claims.

My present invention relates to a process of producing unsymmetrical hepta-carbocyanine dyes and more particularly to a process wherein equivalent quantities of a quaternary ammonium salt of a heterocyclic base and a pentamethine dyestuff of the general formula R2=hydrogen, alkyl or aralkyl,

X =an acid residue such as chlorine or bromine,

are caused to interact in the presence of an alkaline condensing agent and the hexamethine dyestufi thus produced is separated and caused to react with the equivalent quantity of a quaternary ammonium salt of another heterocyclic base in presence of an alkaline condensing agent to produce an unsymmetrical heptacarbocyanine.

It is an object of the present invention to provide a process by which the yield of unsymmetrical heptacarbocyanine is substantially increased. Further objects will be seen from the detailed specification following hereafter.

This application is to be regarded as a continuation in part of my copending application Ser. No. 725,214 filed May 11, 1934.

This invention is based on the observation that the intermediate product for making the unsymmetrical heptacarbocyanine is obtained in particularly good yield if there is used as a component of the reaction the pentamethine-di-(amethyl-phenmorpholide)-bromide of the formula In Germany May 18, 1933 gen bromide and pyridine. The bromide of the pentamethine dyestuff from a-l'llGthYl-DhBHIIlOI- pholine crystallizes in the form of a red powder having a violet iridescence; it is soluble in alcohol and in pyridine to intensely red solutions and is sparingly soluble inwater. The methanol solution shows an absorption maximum of about 5080 A. U. (extremely fiat).

The following example illustrates the invention: 3.05 grams of 2-methyl-benzthiazo1e-ethyliodide mol) and 5.39 grams of pentamethine-di- (umethyl-phenmorpholide) -bromide mol) are dissolved together in cc. of absolute alcohol by prolonged boiling. When dissolution is complete, 3.16 grams of pyridine 0/ mol) are added and heating is continued for 1 hour on the steam bath, whereby the greater part of the alcohol must be evaporated. From time to time a drop of the solution is removed, strongly diluted and observed in the spectroscope. This test shows in the course of the reaction that the fiat band of the pentamethine dyestufi becomes ever weaker Whereas the absorption band of the intermediate product formed, namely at 6080 A. U., becomes ever stronger. When the band of the pentamethine dyestuff has nearly completely vanished, the heating is interrupted. The mixture of pure deep blue color is made up to 50 cc. with boiling alcohol, some concentrated potassium iodide solution is added and the whole is diluted with water added in drops until crystallization sets in. The crystallization is completed by cooling in ice. After some hours the crystals are filtered, whereby a crude product is obtained amounting to about per cent of the theoretical. The violet crystalline mass thus obtained is soluble in alcohol to a pure blue solution and may be used without further purification for making the hepta-carbocyanine dyestufi.

mol of this intermediate product and mol of Z-methyl-benzselenazole ethyl iodide are dissolved together inthesmallest possible quantity of boiling absolute alcohol and there is added to the solution mol of sodium ethylate (dissolved in 15 cc. of alcohol). The solution becomes almost immediately green. The whole is now boiled for a few minutes and cooled; a little aqueous potassium iodide solution is now added, whereupon the unsymmetrical 1:1-diethyl-benzthiobenzseleno-hepta-carbocyanine iodide separates. The crystallization is favored by cooling with ice.

Correspondingly with the production of the intermediate product from 2-methyl-benzthiazole-ethyl-iodide and oc-IIlBthYl phenmorpholine corresponding intermediate products may be obdide 6230 Intermediate product from 2 5 G-trimethyl benzselenazole ethyl iodide 6200' Intermediate product from quinaldine ethyl iodide About 6100 (very flat) Intermediate product from lepidine ethyl iodide About 6400 Intermediate product from 2- methyl-benzthiazole methyl iodide 6100 Intermediate product from 2- methyl-G-ethoxy benzthia zole ethyl iodide About 6150 (very fiat) Intermediate product from 2:5 :G-trimethyl-benzthiazole ethyl iodide 6100 (somewhat depressed) Intermediate product from pnaphthothiazole di methyl sulfate 6250 (somewhat sharp) As will be seen from the foregoing remarks the process according to the present invention is not limited to the reaction of a-meth'yl-phenmo-rpholine with any specific heterocyclic bases and their salts, but is generally applicable in all cases where a base having a methylene group capable of reaction in 2- or l-position is concerned.

In the claims following hereafter the alkaline condensing agent may be any condensing agent used in the art of producing carbocyam'nes. Examples of these condensing agents are for instance alkylamines, oxalkyl amines, piperidine, pyridine, ethanol-amine and alkali alkylates.

What I claim is:

1. A compound corresponding to the following general formula Y being a member of the group consisting of S,Se,-CH=CH; W being a member of the group consisting of alkyl, alkoxy, and a fused-on benzene nucleus; R being alkyl; X being an anion.

2. A compound corresponding to the following formula:

3. A compound corresponding to the following formula:

4. A compound corresponding to the following formula:

OH-CHs \N/ S\ 5. A process of producing hexamethine compounds which comprises reacting equivalent 45 quantities of a quaternary ammonium salt of a 55 in an organic solvent containing an alkaline condensing agent.

WALTER ZEH. 

